From 7bbde67cb2dc52c04bd7020689a1227bddfa1b06 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Wed, 6 Feb 2019 01:12:51 +1100
Subject: [PATCH] lib/utils/printf: Exclude __GI_vsnprintf alias for gcc 9 and
 above.

See issue #4457.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Retrieved from:
https://github.com/micropython/micropython/commit/7bbde67cb2dc52c04bd7020689a1227bddfa1b06]
---
 lib/utils/printf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/utils/printf.c b/lib/utils/printf.c
index 1ceeea39ff..0c21fc4c0a 100644
--- a/lib/utils/printf.c
+++ b/lib/utils/printf.c
@@ -99,9 +99,11 @@ STATIC void strn_print_strn(void *data, const char *str, size_t len) {
     strn_print_env->remain -= len;
 }
 
-#if defined(__GNUC__) && !defined(__clang__)
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 9
 // uClibc requires this alias to be defined, or there may be link errors
 // when linkings against it statically.
+// GCC 9 gives a warning about missing attributes so it's excluded until
+// uClibc+GCC9 support is needed.
 int __GI_vsnprintf(char *str, size_t size, const char *fmt, va_list ap) __attribute__((weak, alias ("vsnprintf")));
 #endif
 
